Melissa asked about the difference between ordinary and tempered
stainless steel wire. Most stainless steel including wire is what
is called 300 series typically type 304 or type 316 which are alloy
of about 18% chromium and 8% nickel with the addition of about 3%
molybdenum for the 316 making it more resistant to corrosion.
Alloys of the 300 series (and 200 series which are somewhat similar)
cannot be hardened (tempered is commonly used incorrectly to mean
this but is actually a softening process) by heat treatment but only
by cold working. The 400 series which has about 12 to 18 % chromium
but little or no nickel can be hardened by heat treating if they
contain sufficient carbon. Typical types for hardening are 410,
420, 430 and 440 which can be hardened to a hardness of up to about
HRC 55 depending on carbon content. This is still fileable as
compared to carbon tool steel which can be hardened to about HRC 65
which is not fileable. 300 series wire is sold cold worked to a
spring temper which could also be what was being referred to. Without
knowing more about the application I really cannot say what the best
wire to use would be. In many environments 300 series alloys have
better corrosion resistance than 400 series but these have adequate
resistance in many environments. I can see that either 300 series
spring temper or 400 series hardened would be more resistant to
damage but would expect that they would because of their higher
strengths be harder to straighten when damaged.
If you want to learn more, please visit our website.
I do not have a good suggestion for a source of hardened 400 series
stainless steel wire but she might try a manufacturer of small coil
springs which are often made in this material. &#;Spring temper&#; type
302/4 and 316 wire is available from MSC down to 0.015" dia. but
should be available from other down to very small sizes but I do not
know what is meant by fine (0.001"?). Hope this is of assistance.
jim (James ME Wallbridge P. Eng.) Libertarian, Metallurgist, Wood &
Metal Worker, Fly Fisher, Resident of Calgary, Canada&#;s new head
office location of choice. Permission is hereby given to use any
herein, as an attributed quote, unless the body of the
message states otherwise.
Fe, <0.03% C, 16-18.5% Cr, 10-14% Ni, 2-3% Mo, <2% Mn, <1% Si, <0.045% P, <0.03% S
Grade 316 is the standard molybdenum-bearing grade, second in importance to 304 amongst the austenitic stainless steels. The molybdenum gives 316 better overall corrosion resistant properties than Grade 304, particularly higher resistance to pitting and crevice corrosion in chloride environments. It has excellent forming and welding characteristics. It is readily brake or roll formed into a variety of parts for applications in the industrial, architectural, and transportation fields. Grade 316 also has outstanding welding characteristics. Post-weld annealing is not required when welding thin sections.
Grade 316L, the low carbon version of 316 and is immune from sensitisation (grain boundary carbide precipitation). Thus it is extensively used in heavy gauge welded components (over about 6mm). Grade 316H, with its higher carbon content has application at elevated temperatures, as does stabilised grade 316Ti.
The austenitic structure also gives these grades excellent toughness, even down to cryogenic temperatures.
Key Properties
These properties are specified for flat rolled product (plate, sheet and coil) in ASTM A240/A240M. Similar but not necessarily identical properties are specified for other products such as pipe and bar in their respective specifications.
Composition
Table 1. Composition ranges for 316 grade of stainless steels.
Grade C Mn Si P S Cr Mo Ni N 316 Min - - - 0 - 16.0 2.00 10.0 - Max 0.08 2.0 0.75 0.045 0.03 18.0 3.00 14.0 0.10 316L Min - - - - - 16.0 2.00 10.0 - Max 0.03 2.0 0.75 0.045 0.03 18.0 3.00 14.0 0.10 316H Min 0.04 0.04 0 - - 16.0 2.00 10.0 - max 0.10 0.10 0.75 0.045 0.03 18.0 3.00 14.0 -
Mechanical Properties
Table 2. Mechanical properties of 316 grade stainless steels.
Grade Tensile Str (MPa) min Yield Str 0.2% Proof (MPa) min Elong (% in 50 mm) min Hardness Rockwell B (HR B) max Brinell (HB) max 316 515 205 40 95 217 316L 485 170 40 95 217 316H 515 205 40 95 217
Note: 316H also has a requirement for a grain size of ASTM no. 7 or coarser.
Physical Properties
Table 3. Typical physical properties for 316 grade stainless steels.
Grade Density(kg/m3) Elastic Modulus (GPa) Mean Co-eff of Thermal Expansion (µm/m/°C) Thermal Conductivity (W/m.K) Specific Heat 0-100 °C (J/kg.K) Elec Resistivity (nΩ.m) 0-100 °C 0-315 °C 0-538 °C At 100 °C At 500 °C 316/L/H 193 15.9 16.2 17.5 16.3 21.5 500 740
Grade Specification Comparison
Table 4. Grade specifications for 316 grade stainless steels.
Grade UNS No Old British Euronorm Swedish SS Japanese JIS BS En No Name 316 S 316S31 58H, 58J 1. X5CrNiMo17-12-2 SUS 316 316L S 316S11 - 1. X2CrNiMo17-12-2 SUS 316L 316H S 316S51 - - - - -
Note: These comparisons are approximate only. The list is intended as a comparison of functionally similar materials not as a schedule of contractual equivalents. If exact equivalents are needed original specifications must be consulted.
Table 5. Possible alternative grades to 316 stainless steel.
Grade Why it might be chosen instead of 316? 316Ti Better resistance to temperatures of around 600-900 °C is needed. 316N Higher strength than standard 316. 317L Higher resistance to chlorides than 316L, but with similar resistance to stress corrosion cracking. 904L Much higher resistance to chlorides at elevated temperatures, with good formability Much higher resistance to chlorides at elevated temperatures, and higher strength than 316
Corrosion Resistance
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Excellent in a range of atmospheric environments and many corrosive media - generally more resistant than 304. Subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 60 °C. Considered resistant to potable water with up to about mg/L chlorides at ambient temperatures, reducing to about 500 mg/L at 60 °C.
316 is usually regarded as the standard &#;marine grade stainless steel&#;, but it is not resistant to warm sea water. In many marine environments 316 does exhibit surface corrosion, usually visible as brown staining. This is particularly associated with crevices and rough surface finish.
Heat Resistance
Good oxidation resistance in intermittent service to 870 °C and in continuous service to 925 °C. Continuous use of 316 in the 425-860 °C range is not recommended if subsequent aqueous corrosion resistance is important. Grade 316L is more resistant to carbide precipitation and can be used in the above temperature range. Grade 316H has higher strength at elevated temperatures and is sometimes used for structural and pressure-containing applications at temperatures above about 500 °C.
Heat Treatment
Solution Treatment (Annealing) - Heat to - °C and cool rapidly. These grades cannot be hardened by thermal treatment.
Welding
Excellent weldability by all standard fusion methods, both with and without filler metals. AS .6 pre-qualifies welding of 316 with Grade 316 and 316L with Grade 316L rods or electrodes (or their high silicon equivalents). Heavy welded sections in Grade 316 require post-weld annealing for maximum corrosion resistance. This is not required for 316L. Grade 316Ti may also be used as an alternative to 316 for heavy section welding.
Machining
A &#;Ugima&#; improved machinability version of grade 316 is available in round and hollow bar products. This machines significantly better than standard 316 or 316L, giving higher machining rates and lower tool wear in many operations.
Dual Certification
It is common for 316 and 316L to be stocked in "Dual Certified" form - mainly in plate and pipe. These items have chemical and mechanical properties complying with both 316 and 316L specifications. Such dual certified product does not meet 316H specification and may be unacceptable for high temperature applications.
Applications
Typical applications include:
Food preparation equipment
particularly in chloride environments.
Laboratory benches & equipment.
Coastal architectural panelling, railings & trim.
Boat fittings.
Chemical containers, including for transport.
Heat Exchangers.
Woven or welded screens for mining, quarrying & water filtration.
Threaded fasteners.
Springs.
Source: Atlas Steels Australia
For more information on this source please visit Atlas Steels Australia
For more information, please visit 316 Stainless Steel Wire.